In the interest of making contact with the representation theory of the AdS\(_3\)  isometry group \(\mathsf {SO}(2,2)\) , it is useful to recast eq. (REF ) into the notation of [1]},
\(0=\bigg (\Box + \ell ^{-2}\big [n/2+1-\eta ^{-2}\big ]\bigg )h_{\alpha (n)}~,\qquad \ell ^{-1}:= 2\mathcal {S}~,\qquad \eta ^{-1}:=\frac{\rho }{2n\mathcal {S}}~.\) 
